The marine waters around Argentina are periodically affected by a range of phytoplankton species that are known producers of paralytic shellfish poisoning (PSP) toxins. The toxic dinoflagellates Alexandrium tamarense and Gymnodinium catenatum have been associated with PSP outbreaks in bivalve molluscs such as mussels. These bivalves are used as a food source by a number of species of carnivorous gastropods, including 2 species of marine snails, Zidona dufresnei and Adelomelon beckii. There is, consequently, a significant risk to consumers of the snails, which can accumulate PSP toxins after predation on the bivalves. Forty-one snail samples of carnivorous snails harvested between 1986 and 2012, representing 2 species (Z. dufresnei and A. beckii), were analyzed for PSP by the reference mouse bioassay (MBA) method and an alternative liquid chromatography with fluorescence detection (LC-FLD) method based on AOAC 2005.06. Sample toxicities determined by the 2 methods correlated well, with no statistical difference in the 2 sets of data. The highest levels of PSP were measured in the viscera of the snails, although PSP was still measured in the edible foot muscle as well above the maximum permitted level in many of the samples. The LC-FLD analysis confirmed the presence of toxins in snail samples returning negative MBA results, therefore showing the advantages of using a more sensitive detection method. The LC-FLD results also enabled the assessment of toxin profiles in each of the snail samples, with data confirming the dominance of saxitoxin (STX) in the majority of snails in comparison with the dominant gonyautoxins quantified in the mussel food source. Conversely, a lower number of Z. dufresnei samples did not exhibit the STX-dominant profile, with a total of 4 different profile clusters determined in the 36 samples analyzed. For A. beckii, these variations were not observed, with a consistent STX-dominant profile measured in each of the samples received. There was no correlation between profile type and the year or season of harvest, although there was some indication that the snails harvested from more southern regions (below 39°S) contained lower relative concentrations of STX on average. Results also confirmed there were no significant differences between the profiles determined in the foot, mucus, and viscera matrices. Overall, the study showed good evidence for another useful confirmatory tool for monitoring levels of PSP in 2 species of carnivorous snails. The generation of toxin profile data has enabled the confirmation of the conversion or selective retention of STX in snail tissues. Whilst the majority of Z. dufresnei samples were found to contain the STX-dominant Although, the remainder of samples were found to contain notably different profiles, the reasons for this remain unknown.
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Vol. 33 • No. 2